java - Android 应用程序在后台调用活动及其片段到前台时崩溃

public class BotListActivity extends FragmentActivity implements DownloadCallback{ // network variables private int mInterval = 5000; //5 seconds default private Handler mHandler; // Keep a reference to the NetworkFragment which owns the AsyncTask object // that is used to execute network ops. private NetworkFragment mNetworkFragment; // Boolean telling us whether a download is in progress, so we don't trigger overlapping // downloads with consecutive button clicks. private boolean mDownloading = false; private String mJSONPost = "{}"; private String TAG = MainActivity.class.getSimpleName(); //Object variables for list view implementation RecyclerView recyclerView; RecyclerAdapter adapter; //string array which holds list data ArrayList<String> botNames = new ArrayList<String>(); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_bot_list); //getSupportActionBar().hide(); // This handler is to conduct network connections every 5 seconds mHandler = new Handler(); startRepeatingTask(); recyclerView = findViewById(R.id.RecyclerView); recyclerView.setLayoutManager(new LinearLayoutManager(this)); adapter= new RecyclerAdapter(this, botNames); recyclerView.setAdapter(adapter); final Button createTradingBotButton = findViewById(R.id.createBotBtn); createTradingBotButton.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // this on click methods pulls up bot configuration activity //onDestroy(); Intent i = new Intent( BotListActivity.this,BotConfiguration.class); startActivity(i); } }); } @Override public void onDestroy() { super.onDestroy(); stopRepeatingTask(); Log.e(TAG, "did the on destroy happen for BotListActivity"); } /** * Runnable class instance is meant to run once via the volatile boolean shutdown variable turning * into a value of true. A temporary while loop is conducted to allow runnable to run once then shut down. */ Runnable mStatusChecker = new Runnable() { volatile boolean shutdown = false; @Override public void run() { while(!shutdown) { try { //network connection to server instantiation mNetworkFragment = NetworkFragment.getInstance(getSupportFragmentManager(), "localhost:8000/api/v1/Trading_Bots", mJSONPost); startDownload(); Log.e(TAG, "network connection ran in botlistactivity"); ; //this function can change value of mInterval. } finally { // 100% guarantee that this always happens, even if // your update method throws an exception Log.e(TAG, "Runnable network class has been stopped.....botlistactivity"); mHandler.postDelayed(mStatusChecker, mInterval); stopRepeatingTask(); shutdown = true; } } } }; void startRepeatingTask() { mStatusChecker.run(); } void stopRepeatingTask() { mHandler.removeCallbacks(mStatusChecker); Log.e(TAG, "stopRepeatingTask for BotListActivity has been completed"); } private void startDownload() { if (!mDownloading && mNetworkFragment != null) { // Execute the async download. mNetworkFragment.startDownload(); mDownloading = true; } } /// TODO's - parse the nested json objects for the json updates that took place @Override public void updateFromDownload(String result){ Log.e(TAG, result); Log.e(TAG, "that was the result'"); mJSONPost = result.replace("HTTP/1.0 200 OK", ""); // Probably want to figure this one out as well Log.e(TAG, mJSONPost); Log.e(TAG, "THAT WAS MJSONPOTST"); if (result != null) { Log.e(TAG, mJSONPost.substring(mJSONPost.indexOf("{"), mJSONPost.lastIndexOf("}") + 1) ); try { int insertIndex = 0; JSONObject JO = new JSONObject(mJSONPost.substring(mJSONPost.indexOf("{"), mJSONPost.lastIndexOf("}") + 1)); JSONArray JA = JO.getJSONArray("Trading_Bots"); // The for loop below retrieves the specefic elements of each json trading object // In this implementation we just need the name of the bot for now botNames.clear(); for (int i = 0; i < JA.length(); i++) { Log.e(TAG, "JSON ARRAY LENGTH = " + JA.length()); //JSONObject JO = (JSONObject) JA.get(i); //only use when extracting specific data of json object other than bot names JSONObject JO2 = new JSONObject(JA.getString(i)); String botName = JO2.keys().next(); botNames.add(insertIndex, botName); Log.e(TAG, "botName = " + botName); } Log.e(TAG, "botNames = " + botNames); adapter.notifyItemInserted(insertIndex); adapter.notifyDataSetChanged(); } catch (final JSONException e) { //mDataText.setText("JSON parsing error"); Log.e(TAG, "Json parsing error: " + e.getMessage()); Log.e(TAG, "Json result = " + result); Log.e(TAG, "json mJSONPost = " + mJSONPost); } } else { Log.e(TAG, "Error... Bot List Activity updateFromDownload not working"); // put error logging output here "no data available" } } @Override public NetworkInfo getActiveNetworkInfo () { ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo(); return networkInfo; } @Override public void finishDownloading () { mDownloading = false; if (mNetworkFragment != null) { mNetworkFragment.cancelDownload(); } } @Override public void onProgressUpdate ( int progressCode, int percentComplete){ switch (progressCode) { // You can add UI behavior for progress updates here. case DownloadCallback.Progress.ERROR: break; case DownloadCallback.Progress.CONNECT_SUCCESS: break; case DownloadCallback.Progress.GET_INPUT_STREAM_SUCCESS: break; case DownloadCallback.Progress.PROCESS_INPUT_STREAM_IN_PROGRESS: break; case DownloadCallback.Progress.PROCESS_INPUT_STREAM_SUCCESS: break; } }

public class NetworkFragment extends Fragment { public static final String TAG = "NetworkFragment"; private static final String URL_KEY = "UrlKey"; private static final String JSON_KEY = "JsonKey"; private DownloadCallback mCallback; private DownloadTask mDownloadTask; private String mUrlString; private String mJSONString; /** * Static initializer for NetworkFragment that sets the URL of the host it will be downloading * from. */ public static NetworkFragment getInstance(FragmentManager fragmentManager, String url, String json_post) { // Recover NetworkFragment in case we are re-creating the Activity due to a config change. // This is necessary because NetworkFragment might have a task that began running before // the config change and has not finished yet. // The NetworkFragment is recoverable via this method because it calls // setRetainInstance(true) upon creation. NetworkFragment networkFragment = (NetworkFragment) fragmentManager .findFragmentByTag(NetworkFragment.TAG); if (networkFragment == null) { networkFragment = new NetworkFragment(); Bundle args = new Bundle(); args.putString(URL_KEY, url); args.putString(JSON_KEY, json_post); networkFragment.setArguments(args); fragmentManager.beginTransaction().add(networkFragment, TAG).setReorderingAllowed(true).commit(); }else{ fragmentManager.beginTransaction().remove(networkFragment).commit(); } return networkFragment; } @Override public void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); // Retain this Fragment across configuration changes in the host Activity. setRetainInstance(true); mUrlString = getArguments().getString(URL_KEY); mJSONString = getArguments().getString(JSON_KEY); } @Override public void onAttach(Context context) { super.onAttach(context); // Host Activity will handle callbacks from task. mCallback = (DownloadCallback)context; } @Override public void onDetach() { super.onDetach(); // Clear reference to host Activity. mCallback = null; } @Override public void onDestroy() { // Cancel task when Fragment is destroyed. Log.e(TAG, "onDestroy() in fragment"); cancelDownload(); super.onDestroy(); } /** * Start non-blocking execution of DownloadTask. */ public void startDownload() { Log.e(TAG, "startDownload in fragment"); cancelDownload(); mDownloadTask = new DownloadTask(); mDownloadTask.execute("http://10.0.2.2:8000/api/v1/Trading_Bots");//mUrlString USE THIS FOR A MORE DIVERSE SERVER } /** * Cancel (and interrupt if necessary) any ongoing DownloadTask execution. */ public void cancelDownload() { if (mDownloadTask != null) { mDownloadTask.cancel(true); mDownloadTask = null; } } /** * Implementation of AsyncTask that runs a network operation on a background thread. */ private class DownloadTask extends AsyncTask<String, Integer, DownloadTask.Result> { /** * Wrapper class that serves as a union of a result value and an exception. When the * download task has completed, either the result value or exception can be a non-null * value. This allows you to pass exceptions to the UI thread that were thrown during * doInBackground(). */ class Result { public String mResultValue; public Exception mException; public Result(String resultValue) { mResultValue = resultValue; } public Result(Exception exception) { mException = exception; } } /** * Cancel background network operation if we do not have network connectivity. */ @Override protected void onPreExecute() { if (mCallback != null) { NetworkInfo networkInfo = mCallback.getActiveNetworkInfo(); if (networkInfo == null || !networkInfo.isConnected() || (networkInfo.getType() != ConnectivityManager.TYPE_WIFI && networkInfo.getType() != ConnectivityManager.TYPE_MOBILE)) { // If no connectivity, cancel task and update Callback with null data. mCallback.updateFromDownload(""); cancel(true); } } } /** * Defines work to perform on the background thread. */ @Override protected Result doInBackground(String... urls) { Result result = null; //String result = ""; if (!isCancelled() && urls != null && urls.length > 0) { String urlString = urls[0]; try { URL url = new URL(urlString); String resultString = downloadUrl(url); if (resultString != null) { result = new Result(resultString); } else { throw new IOException("No response received."); } } catch(Exception e) { result = new Result(e); } } return result; } /** * Send DownloadCallback a progress update. */ @Override protected void onProgressUpdate(Integer... values) { super.onProgressUpdate(values); if (values.length >= 2) { mCallback.onProgressUpdate(values[0], values[1]); } } /** * Updates the DownloadCallback with the result. */ @Override protected void onPostExecute(Result result) { if (result != null && mCallback != null) { if (result.mException != null) { mCallback.updateFromDownload(result.mException.getMessage()); } if (result.mResultValue != null) { mCallback.updateFromDownload(result.mResultValue); } mCallback.finishDownloading(); } } /** * Override to add special behavior for cancelled AsyncTask. */ @Override protected void onCancelled(Result result) { } /** * Given a URL, sets up a connection and gets the HTTP response body from the server. * If the network request is successful, it returns the response body in String form. Otherwise, * it will throw an IOException. */ // might have to pass a json object through here private String downloadUrl(URL url) throws IOException { InputStream stream = null; HttpURLConnection connection = null; String result = null; try { connection = (HttpURLConnection) url.openConnection(); // For this use case, set HTTP method to POST. connection.setRequestMethod("POST"); //Set the Request Content-Type Header Parameter connection.setRequestProperty("content-type", "application/json; utf-8"); //Set Response Format Type connection.setRequestProperty("Accept", "application/json"); // Already true by default but setting just in case; needs to be true since this request // is carrying an input (response) body. noooooo JSONObject json = new JSONObject(mJSONString); try{ //json.put("bot_activated", "true"); //json.put("is_sim_on", "True"); // json.put("profit_reinvest", "100"); // json.put("is_main_on", "Maybe"); } catch(Exception e){ e.printStackTrace(); } // ensure the connection will be used to SEND content connection.setDoOutput(true); DataOutputStream out = new DataOutputStream(connection.getOutputStream()); out.writeBytes(json.toString()); out.flush(); out.close(); int status = connection.getResponseCode(); BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream())); String inputLine; StringBuilder content = new StringBuilder(); while ((inputLine = in.readLine()) != null) { Log.e("appendage", content.toString()); content.append(inputLine); } in.close(); result = content.toString(); } /*Ths is for GET requests // Open communications link (network traffic occurs here). connection.connect(); publishProgress(DownloadCallback.Progress.CONNECT_SUCCESS); int responseCode = connection.getResponseCode(); if (responseCode != HttpsURLConnection.HTTP_OK) { throw new IOException("HTTP error code: " + responseCode); } // Retrieve the response body as an InputStream. stream = connection.getInputStream(); publishProgress(DownloadCallback.Progress.GET_INPUT_STREAM_SUCCESS, 0); if (stream != null) { // Converts Stream to String with max length of 500. result = readStream(stream, 500); publishProgress(DownloadCallback.Progress.PROCESS_INPUT_STREAM_SUCCESS, 0); } /*catch ( MalformedURLException e){ e.printStackTrace();; } catch (IOException e){ e.printStackTrace(); } catch (JSONException e) { e.printStackTrace(); }*/ catch (JSONException e) { e.printStackTrace(); } finally { // Close Stream and disconnect HTTPS connection. if (stream != null) { stream.close(); } if (connection != null) { connection.disconnect(); } } Log.e("finally", "what"); Log.e("HEY", result); return result; } /** * Converts the contents of an InputStream to a String. */ private String readStream(InputStream stream, int maxLength) throws IOException { String result = null; // Read InputStream using the UTF-8 charset. InputStreamReader reader = new InputStreamReader(stream, "UTF-8"); // Create temporary buffer to hold Stream data with specified max length. char[] buffer = new char[maxLength]; // Populate temporary buffer with Stream data. int numChars = 0; int readSize = 0; while (numChars < maxLength && readSize != -1) { numChars += readSize; int pct = (100 * numChars) / maxLength; publishProgress(DownloadCallback.Progress.PROCESS_INPUT_STREAM_IN_PROGRESS, pct); readSize = reader.read(buffer, numChars, buffer.length - numChars); } if (numChars != -1) { // The stream was not empty. // Create String that is actual length of response body if actual length was less than // max length. numChars = Math.min(numChars, maxLength); result = new String(buffer, 0, numChars); } return result; } } }